JP7813151B2 - transmission - Google Patents

Description

The present invention relates to a transmission that transmits power from a vehicle's driving power source to the wheels.

For example, a transmission such as an automatic transmission mounted on a vehicle such as an automobile switches between a forward state and a reverse state by switching between engagement and disengagement of frictional engagement elements such as clutches and brakes.
In a transmission in which a driver or other passenger manually selects a range, a fluid path switching valve (manual valve) that operates in conjunction with a range selection operating unit such as a select lever is used to switch between engagement and disengagement of frictional engagement elements.

The transmission is also provided with a parking lock mechanism that mechanically locks the output shaft to prevent the vehicle from moving when a non-driving range (typically a parking range) is selected.
The parking lock mechanism, for example, has a parking gear on the output shaft or on a shaft portion that is linked to the output shaft, and locks the output shaft by engaging a parking pawl with a recess in the parking gear when the range is switched to the non-driving range.

In the transmission described above, when the transmission is switched from a driving range, such as reverse range, to a non-driving range in which the parking lock mechanism is activated, an abnormal noise (tooth rattle) caused by the parking gear hitting the parking pawl can become a problem.
This type of abnormal noise occurs when the engine torque twists various shaft components in the power transmission path while the vehicle is stopped, causing the reverse frictional fastening element to be released, causing the parking gear to rotate suddenly and ejecting the parking pawl.

For example, Patent Document 1 (JP-A-2003-135999) describes a technology related to a vehicle transmission, in which a manual valve is provided in a hydraulic control device of an automatic transmission, and the manual valve establishes a reverse range by connecting an oil passage to a reverse range achieving hydraulic circuit when in the reverse position, and connects the reverse range achieving hydraulic circuit to a drain oil passage when in the parking position. It also describes that when the manual valve is shifted from reverse to parking, the oil passage leading to the friction engagement device involved in generating the reverse range is connected to the drain oil passage, and the pressurized oil is slowly discharged through this orifice, thereby suppressing gear slapping noise.
Patent Document 2 describes that by providing a pressure-maintaining valve between the drain oil passages of the forward clutch and reverse brake and the drain port open to the atmosphere, and adjusting the flow rate passing through the orifice, the hydraulic oil of the reverse brake is drained slowly at an appropriate speed, thereby preventing select shock when selecting from R range to P range.
Patent Document 3 describes the provision of an electromagnetic switching valve at the drain port of a manual valve that has a supply port that communicates with a hydraulic power source, a discharge port that generates hydraulic pressure according to range switching for forward or reverse drive, and a drain port that opens the drain.The electromagnetic switching valve is connected to a first drain oil passage with an orifice inserted on one side and a second drain oil passage on the other side, and it describes that by selecting the first drain oil passage in the parking range, it is possible to reduce the meshing impact noise of the parking mechanism when switching from the forward or reverse range to the P range.

Registered Utility Model No. 2582881 JP 2020-41558 A Japanese Utility Model Application Laid-Open Publication No. 3-125945

As described in Patent Documents 1 and 2, when an orifice is used to delay oil discharge from a frictional engagement element for reverse gear, the orifice diameter is restricted by hardware specifications in the region where the oil drainage speed becomes a bottleneck, raising concerns that noise may not be effectively suppressed over a wide range. For example, if the orifice diameter is made excessively small, the frictional engagement element may not be properly released when the non-driving range is selected at low temperatures, raising concerns about creep in the non-driving range.
Furthermore, as described in Patent Document 3, when an electromagnetic switching valve is provided, the structure becomes complicated and the cost increases.
In view of the above-mentioned problems, an object of the present invention is to provide a transmission with a simple configuration that effectively suppresses abnormal noise when switching from a driving range to a non-driving range.

In order to solve the above-mentioned problems, a transmission according to one aspect of the present invention is a transmission that can switch between a drive range in which a frictional engagement element provided in a power transmission path from a drive power source to drive wheels is engaged, and a non-drive range in which the frictional engagement element is disengaged, and has a supply port connected to a hydraulic supply source, a frictional engagement element port connected to the frictional engagement element, and a drain port for discharging hydraulic oil returning from the frictional engagement element port, and includes a range switching valve that communicates the supply port and the frictional engagement element port in the drive range and closes the drain port, a supply control valve provided between the hydraulic supply source and the supply port, and a non-drive range in which the frictional engagement element is disengaged from the drive range. The vehicle includes a range switch detection unit that detects switching to the non-driving range, a control unit that controls the supply control valve in response to an output of the range switch detection unit, and a parking lock mechanism that transitions from a released state that allows rotation of the drive wheels to a locked state that locks rotation of the drive wheels in response to switching from the driving range to the non-driving range, wherein the range switch valve connects the supply port and the drain port in the non-driving range, and the control unit holds the supply control valve in an open state after detecting switching from the driving range to the non-driving range until the parking lock mechanism transitions from the released state to the locked state.
According to this, when switching from the driving range to the non-driving range, hydraulic oil continues to flow from the supply port to the drain port, interfering with the hydraulic oil flowing from the frictional engagement element to the drain port via the range switching valve, slowing down the discharge speed of the hydraulic oil from the frictional engagement element.
This delays the time it takes for the frictional engagement elements to transition from an engaged state to a released state, preventing the various shaft components within the transmission from rotating suddenly and reducing the generation of abnormal noise from the parking lock mechanism.

In the present invention, the control unit can be configured to, after detecting a switch from the driving range to the non-driving range, reduce the opening of the supply control valve or fully close it after a predetermined delay time has elapsed that is longer than the time it takes for the parking lock mechanism to transition from the released state to the locked state.
According to this, by reducing the opening of the supply control valve or fully closing it after the parking lock mechanism has transitioned to a locked state, it is possible to prevent a continuous decrease in hydraulic pressure in hydraulic circuits other than those related to the range change valve.

As described above, the present invention provides a transmission with a simple configuration that effectively suppresses abnormal noise when switching from the driving range to the non-driving range.

1 is a diagram showing the configuration of a powertrain of a vehicle having an embodiment of a transmission to which the present invention is applied; 2 is a schematic diagram showing the parking lock mechanism of the transmission of FIG. 1 as viewed from the axial direction of the drive pinion shaft. FIG. FIG. 2 is a cross-sectional view of a manual valve provided in the transmission of the embodiment, illustrating a state in which a reverse range is selected. FIG. 2 is a cross-sectional view of a manual valve provided in the transmission of the embodiment, showing a state in which a parking range is selected. FIG. 10 is a cross-sectional view of a manual valve provided in a transmission that is a comparative example of the present invention, showing a state in which a parking range is selected. FIG. 10 is a diagram showing an example of changes in reverse clutch oil pressure and linear solenoid valve oil pressure when switching from reverse range to parking range in the transmissions of the embodiment and the comparative example.

Hereinafter, an embodiment of a transmission to which the present invention is applied will be described.
The transmission of the embodiment is mounted on a vehicle such as a passenger car having a longitudinally mounted engine as a power source for driving, for example.
FIG. 1 is a diagram showing the configuration of a power train of a vehicle having a transmission according to an embodiment of the present invention.
For ease of understanding, FIG. 1 shows a simplified skeleton diagram of the transmission that only shows the power transmission path to the front wheels FW (drive wheels) when the vehicle is moving backward (when the reverse range (R range) is selected), and does not show the power transmission path when the vehicle is moving forward (when the drive range (D range) is selected), the speed change mechanism, an AWD transfer that distributes driving force to the rear wheels (not shown), etc.

The powertrain 1 includes an engine 10, a transmission 20, a drive shaft 30, and the like.
The engine 10 is an internal combustion engine such as a gasoline engine.
The rotational output of the engine 10 is transmitted to the transmission 20 via a starting device such as a torque converter.

The transmission 20 is a power transmission device that transmits the rotational output of the engine 10 to the front wheels FW via a drive shaft 30 .
The transmission 20 includes an input shaft 21, a reverse clutch 22, a drive gear 23, a drive pinion shaft 24, a driven gear 25, a pinion gear 26, a ring gear 27, a parking gear 28, a parking pawl 29, and the like.

The input shaft 21 is an input shaft to which the rotational output of the engine 10 is input via a starting device.
The reverse clutch 22 is a frictional engagement element provided in the middle portion of the input shaft 21 .
The reverse clutch 22 is engaged when the reverse range is selected and the vehicle is traveling backward, and is disengaged in other states.

The drive gear 23 is a helical gear provided at the end of the input shaft 21 opposite to the engine 10 side.
The drive gear 23 cooperates with the driven gear 25 to transmit power from the input shaft 21 to the drive pinion shaft 24 .

The drive pinion shaft 24 is a rotation shaft that is arranged parallel to the input shaft 21 .
The drive pinion shaft 24 transmits the power transmitted from the input shaft 21 to the ring gear 27 .

The driven gear 25 is a helical gear provided at the middle portion of the drive pinion shaft 24 .
The driven gear 25 meshes with the drive gear 23 of the input shaft 21 to transmit power.

The pinion gear 26 is provided at the end of the drive pinion shaft 24 on the engine 10 side, and meshes with a ring gear 27 .
The pinion gear 26 and the ring gear 27 work together to convert the rotational direction around an axis along the vehicle width direction, and also function as a final reduction gear that reduces the speed at a predetermined final reduction ratio.
The rotation of the ring gear 27 is transmitted to the front wheels FW via a drive shaft 30 .
The drive shaft 30 has a CV joint and functions to transmit rotation in a bendable state in response to the suspension stroke and the steering of the front wheels FW.

The parking gear 28 and the parking pawl 29 cooperate to form a parking lock mechanism.
The parking lock mechanism prevents the vehicle from moving by restricting the rotation of the drive pinion shaft 24 when the parking range is selected.
FIG. 2 is a schematic diagram showing the parking lock mechanism of the transmission of FIG. 1 as viewed from the axial direction of the drive pinion shaft.
FIG. 2(a) shows a state in which the engaging projection of the parking pawl contacts the outer peripheral edge of the parking gear (a state immediately before transitioning to the locked state), and FIG. 2(b) shows the locked state.
The parking gear 28 is a gear provided at the end of the drive pinion shaft 24 opposite to the pinion gear 26 side (engine 10 side).
The parking gear 28 has recesses on its outer periphery that are arranged at equal intervals in the circumferential direction and engage with the parking pawls 29 .

The parking pawl 29 restricts (locks) the rotation of the parking gear 28 and prevents the vehicle from moving by inserting and engaging an engaging protrusion 29a into a recess in the parking gear 28 in response to the driver's operation to select the parking range.
As shown in FIG. 2, the parking pawl 29 is supported so as to be swingable (rotatable) about a rotation shaft 29b.
The rotating shaft 29b is fixed to a housing (transmission case) of the transmission 1 (not shown).

The parking pawl 29 moves in conjunction with a range selection operating part such as a selector lever between a release position in which the engagement protrusion 29a is separated from the parking gear 28 and a lock position in which the engagement protrusion 29a engages with a recess in the parking gear 28.
Here, when the engaging protrusion 29a abuts against the outer peripheral edge of the parking gear 28 as shown in Figure 2(a), the parking gear 28 rotates and the positions of the engaging protrusion 29a and the recess of the parking gear 28 match, the engaging protrusion 29a is inserted into the recess as shown in Figure 2(b), and a locked state is established.
However, if the parking gear 28 rotates at a high speed, the engaging projection 29a does not properly engage with the recess and is repelled by the parking gear 28, causing an abnormal noise (clashing noise).
This embodiment aims to suppress such abnormal noise, and this point will be explained in detail later.

The transmission 20 described above has a hydraulic circuit, which will be described below, for switching between engagement and disengagement of various frictional engagement elements such as a reverse clutch, and for changing the gear ratio of a transmission mechanism such as a chain-type CVT.
The hydraulic circuit operates using automatic transmission fluid (hereinafter referred to as "oil"), which serves as both lubricating oil and hydraulic oil (pressure oil).

The hydraulic circuit includes a manual valve 100, which is a range switching valve that selects and switches the driving range of the transmission 20 from a drive range (D range), a neutral range (N range), a reverse range (R range), and a parking range (P range).
The drive range is a driving range used when traveling forward.
The neutral range is a non-driving range in which the parking lock mechanism is released.
The reverse range is a driving range used when moving backward.
The parking range is a non-driving range in which the parking lock mechanism is locked.

The manual valve 100 is linked to a selector lever (not shown) provided in the vehicle cabin and operated by the driver to select a range, by means of a mechanical linking means such as a Bowden wire.
FIG. 3 is a cross-sectional view of the manual valve provided in the transmission of the embodiment, showing a state in which the reverse range is selected.
FIG. 4 is a cross-sectional view of a manual valve provided in the transmission of the embodiment, showing a state in which the parking range is selected.
3 and 4, the flow of oil is indicated by dashed arrows, and the flow of electrical signals is indicated by solid arrows (the same applies to FIG. 5, which will be described later).

The manual valve 100 includes a sleeve 110, a spool valve 120, and the like.
The sleeve 110 is a cylindrical member fixed to a transmission case, which is the housing of the transmission 20 .
The sleeve 110 has a cylindrical through-hole formed on its inner diameter side, into which the spool valve 120 is inserted.
The sleeve 110 is provided with a drain port 111, a forward clutch port 112, a supply port 113, a reverse clutch port 114, a drain port 115, etc., in this order from one axial end (the left side in Figure 3, etc.).

The drain port 111 is a port that discharges oil returning from a forward clutch 250 (described later) from inside the sleeve 110 (discharges it into the transmission case) in response to switching from the drive range to another range.
The forward clutch port 112 is a port that supplies oil from the inside of the sleeve 110 to a forward clutch 250, which will be described later, when the drive range is selected (when the vehicle is moving forward).
Further, the forward clutch port 112 functions as a flow path for returning oil from the forward clutch 250 to the inside of the sleeve 110 in response to a transition from the drive range to another range.

The supply port 113 is a port through which oil pressurized and discharged by the oil pump 230 is introduced into the inside of the sleeve 110 .
The reverse clutch port 114 is a port (frictional engagement element port) that supplies oil from the inside of the sleeve 110 to the reverse clutch 22 when the reverse range is selected (when the vehicle is moving backward).
Furthermore, the reverse clutch port 114 functions as a flow path for returning oil from the reverse clutch 22 to the inside of the sleeve 110 in response to a transition from the reverse range to another range.
The drain port 115 is a port that discharges oil returning from the reverse clutch 22 from inside the sleeve 110 (discharges it into the transmission case) in response to switching from the reverse range to another range.

The spool valve 120 is a valve element that is inserted into the inner diameter side of the sleeve 110 and switches between opening and closing of each port of the sleeve 110 .
The spool valve 120 is displaced relative to the sleeve 110 in the axial direction of the cylinder in response to a range selection operation using a selector lever (not shown).
The spool valve 120 is formed in an axial shape concentric with the inner peripheral surface of the sleeve 110, and lands 121, 122, and 123 are provided sequentially along the axial direction from the drain port 111 side (left side in Figures 3 and 4) to the drain port 115 side (right side in Figure 4).
The lands 121, 122, and 123 are formed into a cylindrical shape by partially expanding the outer diameter of the spool valve 120 relative to the shaft portion other than the lands.
The outer peripheral surfaces of the lands 121, 122, and 123 face the inner peripheral surface of the sleeve 110 with a small clearance therebetween, making it possible to seal in oil.
Between lands 121 and 122, and between lands 122 and 123, there is a gap between the outer surface of spool valve 120 and the inner surface of sleeve 110, allowing oil to pass through this gap.

In the reverse range state shown in FIG. 3, the land 121 blocks communication between the supply port 113 and the forward clutch port 112 (ie, does not allow communication between them).
The end face of the land 122 on the land 121 side is disposed between the reverse clutch port 114 and the drain port 115 in the axial direction of the sleeve 110. At this time, the supply port 113 and the reverse clutch port 114 are in communication with each other.
As a result, oil is supplied to the reverse clutch 22 as shown by the dashed arrow in FIG.
In addition, the supply port 113 and the drain port 115 are blocked.

4, the land 122 is positioned so as to overlap the supply port 113 in the axial direction of the sleeve 110. The land 122 separates the supply port 113 from the drain port 111 and the forward clutch port 112.
The land 121 is provided with a notch 124 formed by recessing the outer circumferential surface in a groove shape.
The notch 124 is formed so as to communicate from the end face of the land 121 on the land 122 side to the outer circumferential surface.
The notch 124 allows communication between the supply port 113 and the drain port 115 when the parking range is selected.
The land 122 closes the opening at the end of the sleeve 110 on the drain port 115 side (the right end in FIG. 4).
The land 123 is in a state of being drawn out to the outside of the sleeve 110 .

As shown in FIGS. 3 and 4, the transmission 20 further includes a transmission control unit 210, a range detection switch 220, an oil pump 230, a linear solenoid valve 240, a forward clutch 250, and the like.
The transmission control unit (TCU) 210 is an electronic control device (control unit) that comprehensively controls the transmission 20 and its accessories.
The transmission control unit 210 can be configured as a microcomputer having, for example, an information processing section such as a CPU, a storage section such as a RAM or a ROM, an input/output interface, and a bus connecting these.
The transmission control unit 210 controls the gear ratio of the transmission mechanism (not shown) in the transmission 20, the fastening force of the lock-up clutch (not shown), and, in the case of an AWD vehicle, the fastening force of the transfer clutch (not shown).
The transmission control unit 210 also has a function of controlling the opening of the linear solenoid valve 240 in accordance with the output of the range detection switch 220 and the like.

A range detection switch 220 is connected to the transmission control unit 210 .
The range detection switch 220 is a range switching detection unit that detects the range selected by the driver in the transmission 20 and outputs a range signal indicating the detected range.
The range detection switch 220 may be, for example, a physical switch that detects the range based on the position of the spool valve 120 of the manual valve 100 or the position of the select lever.

The oil pump 230 is a hydraulic pressure supply source that pressurizes oil and supplies it to the linear solenoid valve 240 and other hydraulic elements (not shown).
The linear solenoid valve 240 is a supply control valve that supplies oil pumped from the oil pump 230 to the supply port 113 of the manual valve 100 .
The linear solenoid valve 240 can control the oil pressure and amount of oil introduced into the supply port 113 of the manual valve 100 by adjusting the opening degree in response to a command from the transmission control unit 210 .

The forward clutch 250 is a frictional engagement element provided midway along a power transmission path (not shown) during forward movement.
The forward clutch 250 is engaged when the drive range is selected and the vehicle is traveling forward, and is disengaged in other states.

In this embodiment, after the range detection switch 220 detects a switch from the reverse range to the parking range, the transmission control unit 210 maintains the linear solenoid valve 240 in an open state (typically in a fully open state) for a predetermined time, and after the parking gear 28 and the parking pawl 29 engage and the parking lock mechanism transitions to a locked state, performs delay control to reduce the opening of the linear solenoid valve 240 (typically to a fully closed state).
Here, the specified time is set to be longer than the time from when the parking pawl 29 starts to be driven to engage with the parking gear 28 in response to switching to the parking range until the engagement is completed (the time it takes for the parking lock mechanism to transition from the released state to the locked state).

The effects of the above-described embodiment will be described below in comparison with a comparative example of the present invention, which will be described below.
In the comparative example, the same parts as those in the embodiment are denoted by the same reference numerals and the description thereof will be omitted, and the differences will be mainly described.
FIG. 5 is a cross-sectional view of a manual valve provided in a transmission that is a comparative example of the present invention, showing a state in which the parking range is selected.
In the transmission of the comparative example, the notch 124 is not formed in the land 121, and when the parking range is selected, the supply port 113 and the drain port 115 are blocked.
In the comparative example, in response to detection of switching to the parking range, the transmission control unit 210 immediately fully closes the linear solenoid valve 240 .

FIG. 6 is a diagram showing an example of changes in the reverse clutch oil pressure and the linear solenoid valve oil pressure when switching from the reverse range to the parking range in the transmissions of the embodiment and the comparative example.
In FIG. 6, the horizontal axis represents time, and the vertical axis represents, from the top, the range selection state (output of range detection switch 220), the oil pressure of reverse clutch 22, and the oil pressure discharged from linear solenoid valve 240, respectively.
Moreover, the oil pressures of the embodiment are indicated by solid lines, and the oil pressures of the comparative example are indicated by dashed lines.
For ease of understanding, the dashed lines are shown slightly offset where the hydraulic pressures of the embodiment and the comparative example are nearly identical, but in reality, the difference between these hydraulic pressures can be ignored.

In the comparative example, in response to detection of a switch from the reverse range to the parking range, no delay time is provided, the linear solenoid valve is immediately fully closed, and the discharge oil pressure is set to zero.
At this time, in the manual valve 100, as shown in FIG. 5, the supply port 113 is closed and the reverse clutch port 114 and the drain port 115 are in communication with each other.
The oil Or that has returned from the reverse clutch 22 to the reverse clutch port 114 passes through the inside of the sleeve 110 and is discharged from the drain port 115 .
As a result, the hydraulic pressure of the reverse clutch 22 drops in a short time, and the reverse clutch 22 rapidly transitions from an engaged state to a released state.
At this time, if the input shaft 21, drive pinion shaft 24, etc., which have been twisted by the torque of the engine 10, suddenly rotate in the direction of untwisting, the parking gear 28 may repel the engaging protrusion 29a of the parking pawl 29, causing an abnormal noise (tooth rattle).

In contrast to this, in this embodiment, as shown in FIG. 4, when the parking range is selected, the supply port 113 and the drain port 115 are in communication with each other via the notch 124 .
Furthermore, after switching to parking range, the transmission control unit 210 keeps the linear solenoid valve 240 open for a predetermined time, during which time oil O continues to flow from the oil pump 230 to the drain port 115, sequentially passing through the linear solenoid valve 240, the supply port 113, and the inside of the sleeve 110.
At this time, the oil Or returning from the reverse clutch 22 to the reverse clutch port 114 interferes with the flow of the oil O, and the speed at which the oil Or is discharged from the drain port 115 slows down.
Therefore, in the embodiment, the rate at which the oil pressure of the reverse clutch 22 decreases (the rate at which the clamping force decreases) after switching to the parking range is slower than in the comparative example, and the drag friction of the reverse clutch 22 causes the rotation of the input shaft 21 and the drive pinion shaft 24 due to the torsional torque to become slower.
This prevents the parking gear 28 from bouncing off the engaging projection 29a of the parking pawl 29, thereby suppressing noise associated with the operation of the parking lock mechanism.

As described above, according to this embodiment, the following effects can be obtained.
(1) When switching from the reverse range to the parking range, oil O continues to flow from the supply port 113 to the drain port 115 for a predetermined period of time, which interferes with the oil Or flowing from the reverse clutch 22 to the drain port via the inside of the sleeve 110, slowing down the discharge speed of the oil Or from the reverse clutch 22.
This delays the time it takes for the reverse clutch 22 to transition from an engaged state to a released state, preventing the drive pinion shaft 24 and other components from rotating suddenly and reducing the generation of abnormal noise from the parking lock mechanism.
(2) By fully closing the linear solenoid valve 240 after the parking lock mechanism (parking gear 28, parking pawl 29) has transitioned to the locked state, it is possible to prevent a continuous decrease in hydraulic pressure in hydraulic circuits other than those related to the manual valve 100.

(Modification)
The present invention is not limited to the above-described embodiment, and various modifications and variations are possible, and these are also within the technical scope of the present invention.
(1) The configurations of the transmission, power train, vehicle, etc. are not limited to those in the above-described embodiment and can be modified as appropriate.
The shape, structure, material, manufacturing method, function, arrangement, quantity, etc. of each of the members and components that make up these can be changed as appropriate.
(2) The configuration of the flow path that connects the oil supply source and the drain port when the parking range is selected is not limited to a notch formed in the land of the spool valve as in the embodiment, and may be in another form.
(3) In the embodiment, switching from the reverse range to the parking range has been described. However, the present invention can also be applied to switching from the drive range to the parking range.

REFERENCE SIGNS LIST 1 Power train 10 Engine 20 Transmission 21 Input shaft 22 Reverse clutch 23 Drive gear 24 Drive pinion shaft 25 Driven gear 26 Pinion gear 27 Ring gear 28 Parking gear 29 Parking pawl 29a Engagement protrusion 29b Rotating shaft 30 Drive shaft FW Front wheel 100 Manual valve 110 Sleeve 111 Drain port 112 Forward clutch port 113 Supply port 114 Reverse clutch port 115 Drain port 120 Spool valve 121, 122, 123 Land 124 Notch 210 Transmission control unit 220 Range detection switch 230 Oil pump 240 Linear solenoid valve 250 Forward clutch O Oil

Claims (2)

A transmission capable of switching between a driving range in which a frictional engagement element provided in a power transmission path from a driving power source to a drive wheel is engaged and a non-driving range in which the frictional engagement element is disengaged,
a range switching valve having a supply port connected to a hydraulic supply source, a frictional engagement element port connected to a frictional engagement element, and a drain port for discharging hydraulic oil returning from the frictional engagement element port, the range switching valve communicating the supply port with the frictional engagement element port and closing the drain port in the travel range;
a supply control valve provided between the hydraulic supply source and the supply port;
a range switch detection unit that detects switching from the driving range to the non-driving range;
a control unit that controls the supply control valve in response to an output of the range switching detection unit;
a parking lock mechanism that transitions from a released state in which rotation of the drive wheels is permitted to a locked state in which rotation of the drive wheels is locked in response to switching from the drive range to the non-drive range,
the range switching valve communicates the supply port with the drain port in the non-travel range;
the control unit, after detecting the switch from the driving range to the non-driving range, holds the supply control valve in an open state until the parking lock mechanism transitions from the released state to the locked state. 2. The transmission according to claim 1, wherein, after detecting the switch from the drive range to the non-drive range, the control unit reduces the opening of the supply control valve or fully closes the supply control valve after a predetermined delay time has elapsed that is longer than the time it takes for the parking lock mechanism to transition from the released state to the locked state.